Field device in measurement and automation technology comprising a galvanic isolation device

1. A field device of measurement and automation technology, comprising: a housing having a housing wall and a first housing chamber, wherein the first housing chamber is bounded at least partially by the housing wall; a measurement electronics adapted to produce a measurement signal representing a measured variable; a data transmission means; an electronic operating circuit, which is arranged in the first housing chamber and is adapted to operate the data transmission means and the measurement electronics as well as to convert the measurement signal into a measured value, wherein the data transmission means is arranged outside of the first housing chamber and is adapted to exchange data with the electronic operating circuit of the field device; an electrical signal line connecting the data transmission means and the electronic operating circuit, wherein the electrical signal line includes a plurality of electrical conductors adapted to transfer a data signal between the data transmission means and the electronic operating circuit; a first electrical conductor adapted to lead a first electrical current transporting the data signal and a second electrical conductor adapted to lead a second electrical current transporting the data signal, wherein the second electrical current is opposite to the first electrical current; and an isolation device adapted to isolate a first, data transmission means side, signal line section galvanically from a second, operating electronics side, signal line section, wherein each electrical conductor has a first, data transmission means side, conductor section and a second, galvanically isolated, operating electronics side, conductor section, wherein the conductor sections are arranged on the isolation device, wherein the isolation device includes an electromagnetically transparent plate having a first lateral surface and a second lateral surface parallel to the first lateral surface, wherein on the isolation device the conductor sections of the first signal line section are arranged on the first lateral surface and wherein the conductor sections of the second signal line section are arranged on the second lateral surface, wherein each first conductor section is opposite the corresponding second conductor section along a lateral surface normal, and wherein the plate has at least a minimum thickness or dielectric strength required by a safety standard.

2. The field device as claimed in claim 1 , wherein the safety standard is a standard from the following list: Product safety standard IEC 60664-1 of the year 2007 or Ex-d standard IEC 60079-1 of the year 2014, or Ex-i standard IEC 60079-11 of the year 2011 or IEC 61010-1 of the year 2010.

3. The field device as claimed in claim 1 , wherein the housing includes a second housing chamber that is separated from the first housing chamber by an inner wall of the housing, and wherein the inner wall has a second signal feedthrough through which the signal line extends.

4. The field device as claimed in claim 3 , wherein the data transmission means includes an antenna apparatus adapted to receive and/or to transmit high frequency signals, wherein the antenna apparatus is arranged on an outside of the housing wall, and wherein the signal line extends through a first signal feedthrough in the housing wall.

5. The field device as claimed in claim 4 , wherein the housing and the first signal feedthrough, and the second signal feedthrough, are embodied pressure-resistantly according to an Ex-d standard, including IEC 60079-1, and wherein the isolation device is arranged in the first signal feedthrough or second signal feedthrough and is cast pressure-resistantly by means of a potting material.

6. The field device as claimed in claim 4 , wherein the field device includes an enclosure of the isolation device, in which enclosure the isolation device is arranged, wherein the enclosure is arranged in the first signal feedthrough, or in the second signal feedthrough, wherein an outside of the enclosure is connected securely with the first signal feedthrough, or with the second signal feedthrough, wherein the isolation device is cast pressure-resistantly in the enclosure by means of a potting material.

7. The field device as claimed in claim 1 , wherein each electrical conductor includes a first, data transmission means side, conductor section and a second, galvanically isolated, operating electronics side, conductor section.

8. The field device as claimed in claim 1 , wherein the first electrical conductor and the second electrical conductor extend on the lateral surfaces in parallel with one another, and/or wherein the conductor sections of the first signal line section on the first lateral surface extend in parallel with the conductor sections of the second signal line section on the second lateral surface.

9. The field device as claimed in claim 1 , wherein two second electrical conductors are associated with the first electrical conductor, and the second electrical conductors are arranged on opposite sides of the first electrical conductor.

10. The field device as claimed in claim 1 , wherein the plate is composed of a dielectric material, wherein the dielectric material comprises at least one material from the following groups of materials: ceramics, plastics, and glass.

11. The field device as claimed in claim 1 , wherein the electrical conductors in the region of the isolation device are prepared by means of a printing or etching method on the lateral surfaces of the plate.

12. The field device as claimed in claim 1 , wherein the electrical conductors on the lateral surfaces are metallic and comprise at least one of the following materials: copper, silver, aluminum, iron, or an alloy containing at least one of these elements.

13. The field device as claimed in claim 1 , wherein a length of the conductor sections in the region of the isolation device in an overlap region is at least 5 mm and at most 150 mm.

14. The field device as claimed in claim 1 , wherein the data signal has a frequency of at least 0.25 GHz and at most 10 GHz.

15. The field device as claimed in claim 14 , wherein a wavelength of the data signal is greater by a factor F than the length of the conductor sections in the region of the galvanic isolation device, wherein F is greater than 1 and less than 5.5.